Comment on this series of patches (PATCH 2-9)

This concludes easiest part of autodetecting compile configuration using autoconf generated configure script. Patches needs revision by somebody better versed in autoconf than me.

Autodetection TODO: 
* check for Python (NO_PYTHON) and it's version (WITH_OWN_SUBPROCESS_PY)
  or just "own subprocess.py"
* check for "IPv6 support" and getaddrinfo() (NO_IPV6), latter can be
  easily done in autoconf
* check for "proper iconv support" (NO_ICONV), probably custom check.
* check for USE_PIC, NO_SYMLINK_HEAD and NO_ACCURATE_DIFF, all
  needing custom tests.
* use XXX_SHA1 when NO_OPENSSL, with XXX according to the architecture
  git is compiled for.

Next planned are series of patches allowing to select optional build features and packages from configure script... if somebody else wouldn't do it (hint, hint).

About needing autoconf to build git:

1. Currently using autoconf is totally optional, so one can compile
git as one used to earlier. This results in non-autoconf conventions
in configure.ac

2. configure script generated by autoconf can be treated exactly the
same like html and man documentation generated by asciidoc: use
separate 'configure' branch to store current version of configure
script, and add autogeneration of configure script to the same hook
like generating html and man documentation.